Actions to take as citizens to REDUCE SEVERITY OF FLOODING
SEVERAL FLOODING events took place in 2017 throughout various sections of Jamaica. The most significant event was perhaps the November 22 flooding in Montego Bay, in which just four hours of intense rainfall wreaked havoc in the downtown city centre. These flood events are destructive and result in millions of dollars in losses, repairs, and clean-up. In addition, they pose a substantial risk to life and health. As such, any mitigation action that can be taken to reduce the risk of flooding should be considered, and practiced by all Jamaicans. This article, therefore, touches briefly on some of the actions that we can take as citizens to reduce flooding severity.
WETLAND CONSERVATION
Wetlands refer to any area which is periodically saturated with water. They can be coastal (mangroves and brackish marshes), or located further inland.
They serve many important ecological roles to the surrounding environment, including protection and improvement of water quality, provision for fish and wildlife habitat, and shoreline protection. What is perhaps less known is that wetlands are important systems for flood control. They act as water-detention areas (flood storage) and by so doing, reduce peak flood flows.
Some major wetlands in Jamaica include the Great Morass in St Thomas and the Black River Morass in St Elizabeth. It is crucial that these areas be protected, not only for the critical ecological roles that they play, but also for their role in reducing flooding. The protection and conservation of wetlands falls under the mandate of the National Environment and Planning Agency (NEPA).
All watercourses have a finite carrying-capacity. If there are too many solids being transported by the water in a watercourse or drainage system, the system will be overwhelmed and spillage (or overtopping of the system) will occur. This is particularly relevant when the watercourse constricts, such as at a culvert or bridge. The solids (whether sediment, debris or garbage) will pile up at these structures, impeding the flow of water.
EFFECTS OF CONSTRUCTION
Construction activities are some of the biggest culprits with regard to sediment loading in watercourse or drainage systems. It is imperative that any exposed soil and rocks on a construction site are secured. The application of a soil stabiliser (for example, wood mulch) to bare soil surfaces is an example of an effective measure to protect the soil from water and wind erosion. A silt fence (if properly installed and maintained) is also an excellent measure to put into place. Last, it is critical that the inlets of storm drains collecting runoff from the construction sites are protected.
Deforestation is also a culprit with regard to sediment loading in watercourses. Removal of trees decreases the structural support given to the soil by fine roots. The intertwining of root systems between trees forms a network that holds soil in place. As a tree is cut, roots begin to decay and the reinforcement to soil strength offered by the roots is quickly lost.
The removal of the vegetation, therefore, leads to increased soil erosion and movement. Another consequence of the deforestation process is that unwanted logs or tree trunks are left lying on the ground. These will also wash down into the watercourses, causing severe blockage in many instances.
It is, therefore, important to safeguard forested and vegetated areas as much as possible. Community initiatives to reforest upper sections of watersheds can play a key part in reducing sediment loads that report to the watercourses.